• WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
    Building, troubleshooting and testing of these amplifiers should only be
    performed by someone who is thoroughly familiar with
    the safety precautions around high voltages.

RH84 v2 buzzing

Hello fellow DIYers
I built an RH84 v2 amp, the amp by itself is working fine, it is quiet, no buzz no hums and very little hissing which is not much audible when it's playing something.
I decided to use the RH84 to power the HF section of my active speakers and leave the lower freqs to my trusty Hypex, both amps (RH84 and the Hypex) work fine with no issue on their own, but when I turned them on together both amp start buzzing load, if I turn either off the buzzing will stop but apparently they are not happy working together, sounds like grounding issue ? any ideas ?